Ecological Archives E093-203-A1

Cóilín Minto and Boris Worm. 2012. Interactions between small pelagic fish and young cod across the North Atlantic. Ecology 93:2139–2154. http://dx.doi.org/10.1890/10-2036.1

Appendix A. Review of cod spawning and small pelagic fish feeding overlap.

In the northwest Atlantic, spawning of Georges Bank cod occurs over a protracted period of time between November and May, with peak spawning activity during February and March (ICES 2005, and references therein). Spawning occurs on the eastern (particularly the Northeast Peak) and western parts of the bank; spawning is also noted from the Nantucket Shoals (ICES 2005). Spring bottom trawl surveys show the presence of non-spawning (outside mid-September to mid-October) Gulf of Maine-Georges Bank (GMGB) herring in overlapping areas from 1968–1998 (Overholtz and Friedland 2002). Using specifically designed research surveys, Garrison et al. (2002) established that a significant overlap occurs between pelagic fish such as Atlantic herring and mackerel and larval fish, including cod, on the southern flank of Georges Bank. Gulf of Maine cod spawn during the winter and early spring with a north-south gradient in timing - later spawning occurring in the north (ICES 2005). Spawning predominantly occurs on the western side, particularly in Massachusetts Bay and north of Cape Ann; although spawning also occurs off the coast of Maine (ICES 2005). GMGB herring are found in overlapping areas (Overholtz and Friedland 2002) during the same time of year as cod are spawning.

Unusually, Western and Eastern Scotian Shelf cod have traditionally had spring (February-March) and fall (October-November) spawning components (ICES 2005). Spawning locations are broadly distributed over the region with high activity occurring on Brown's Bank and the mouth of the Bay of Fundy in Spring and inshore along the Nova Scotian coastline from Yarmouth to Halifax Harbour (ICES 2005).

Unfortunately there are at least 4 important Northwest Atlantic cod populations omitted from the herring analyses. These include the eastern Scotian Shelf (4VsW), the western Scotian Shelf and Bay of Fundy (4X), Northern (2J3KL), and the Southern Grand Bank (3NO). Cod assessments were available for the eastern Scotian Shelf and the western Scotian Shelf and Bay of Fundy stocks but the absence of a commercial fishery in the Newfoundland stocks has made difficult formal assessment of absolute abundance. Published herring assessments, providing estimates of absolute abundance, were either not available or covered only a small part of the distributions, e.g. inshore eastern Newfoundland stocks. We could have elected to use survey data in lieu of assessments but these would involve many assumptions that could impinge on the results. It is of note that the cod populations in the general region are at extremely low levels, compared to their historical abundances while the abundance of pelagic species has generally increased (Frank et al. 2005, Bundy and Fanning 2005). However, Shelton et al. (2006) concluded that changes in adult natural mortality rather than the rate of recruitment were responsible for the delayed recovery of cod.

The northwest Atlantic mackerel stock over-winters off Cape Hatteras and then splits into a Northern and Southern component in the Spring. Mackerel show a strong temporal variability in distribution but are broadly distributed within the northwest Atlantic. The potential for spatial overlap of cod spawning and herring and mackerel feeding areas have previously been established in the Northern and Southern Gulf of St. Lawrence (Swain and Sinclair 2000, Duplisea and Robert 2008, and references therein).

In the northeast Atlantic, northeast Arctic and Norwegian coastal cod spawn from mid-February to early May with peak spawning at the end of March and start of April (ICES 2005). Spawning locations for both stocks are mostly near-shore and widely distributed from mid- to northern-Norway. Prominent spawning locations occur near Lofoten and offshore from Vester°alen (ICES 2005). Norwegian spring spawning (NSS) migration patterns have changed in the past 60 years (Dragesund et al. 1997, Kvamme et al. 2003). Currently, adult herring over-winter (October-January) close to Lofoten before spreading out to spawn along the Norwegian coast in February and March (Devold 1963). Juvenile fish spend the early part of their life in the Barents Sea (Dragesund et al. 1997) and feeding along the Norwegian coast. Post-spawning adult herring undertake extensive feeding migrations far out into the Norwegian Sea (Dragesund et al. 1997, Kvamme et al. 2003). The overlap between young cod and feeding herring might therefore be restricted to the early part of the herring life history in the Barents Sea.

Icelandic cod spawn off the south and southwest coast from mid-March to early May (Marteinsdóttir et al. 2000). Eggs and larvae drift around the coast in a clockwise direction to where they settle off the north coast (Marteinsdóttir et al. 2000). Icelandic summer spawning herring migrate in late February from the over-wintering grounds off Snfellsnes and the south coast to feed off the west and east coasts (Óskarsson et al. 2009). The potential for overlap with cod eggs and larvae exists. Capelin have a circumpolar boreal water distribution (Rose 2005). In the North Atlantic, major concentrations occur around Newfoundland and Labrador, north of Iceland and the Barents Sea (Rose 2005). The distribution of feeding in Iceland and the Barents Sea potentially overlap with the presence of early stage cod.

Peak spawning activity occurs in March for West of Scotland cod (ICES 2005). Based on egg survey, trawl, and tagging data, Wright et al. (2006) showed that, during the 1950s, cod eggs were distributed widely in area VIa with particularly high densities in the Minch and north of the Isle of Lewis. These observations were corroborated with recent trawl surveys of ripe fish, which also indicated the importance of the Clyde region Wright et al. (2006). West of Scotland herring aggregations are distributed widely. There is evidence that juvenile herring from this stock migrate into the North Sea (ICES 2009b) but relatively little is known about general migration patterns in this stock. Irish sea cod predominantly spawn in the western Irish Sea between Dublin and Carlingford Lough (ICES 2008a), although spawning also occurs in the north and east of the Isle of Man (Brander 1994, Wright et al. 2006, Fox et al. 2000). Spawning occurs between January and May with the peak spawning activity in March (Brander 1994). Herring in the Northern part of the Irish Sea are typically distributed around the Isle of Man (ICES 2009b). A Mourne fishery in closer proximity to the Irish coast (where cod spawn) does exist but the overlap with cod is potentially minimal. Celtic Sea cod spawn in February-March close inshore off the Southwest of Ireland (ICES 2008b). Spawning also occurs in the Bristol channel in mid- to late-March (Brander 1994). Celtic Sea herring spawn inshore off the south and southwest coast of Ireland in the Autumn and Winter and migrate offshore to summer feeding regions (ICES 2009b). It is possible that the overlap in this region is also minimal.

Fox et al. (2008) consolidated historical and contemporary records of cod spawning locations in the North Sea. Spawning predominantly occurs on the southern and eastern Dogger Bank, the German Bight and to the north in the Moray Firth and east of the Shetland Islands. The timing of spawning is earlier in the southern regions (late January) compared to northern regions (March) (Brander 1994). Based upon the dominant spawning locations, North Sea herring comprise four major sub-components: Shetland, Buchan, Banks and Downs (Bierman et al. 2010). The subcomponents mix to feed between April and June in the northern part of the North Sea (Cushing and Bridger 1966). Given that the spawning of cod is predominantly in the south of the North Sea (Fox et al. 2008) the overlap with feeding herring is potentially small. Although Daan et al. (1985) showed that herring do eat cod and plaice eggs in the early part of the season in the North Sea. Northeast Atlantic mackerel comprise three components: North Sea, Western, and Southern. Western mackerel spawn from March-July along western Europe, particularly on the Porcupine and Great Sole Banks (Lockwood 1988, Uriarte and Lucio 2001). Following spawning, the stock moves up along the Irish coast and west of Scotland to feed in the Norwegian Sea and northern North Sea (Uriarte and Lucio 2001). It is difficult to establish whether significant overlap will occur with eggs and larval cod. Although the western component has been used for all regions here because the North Sea component has never recovered from severe depletion. The western component does dip into the northern part of the north sea.

Kattegat cod spawn between January and March, predominantly in the southeast in the vicinity of Sk¨alderviken, Laholmsbukten, and Falkenburg (Vitale et al. 2008). Herring in this region are grouped under the Western Baltic Spring Spawning herring that migrate out of the Baltic to the Kattegat, Skagerrak and the North Sea to feed. There is a potential for overlap during this time. The Western Baltic cod stock spawn from the January to May with peak spawning in February- April (Bagge et al. 1994). Spawning occurs predominantly in the south of subdivision 22 (ICES 2005). The overlap between WBSS herring and cod eggs has been studied intensely (Köster and Möllmann 2000) with the conclusion that there is a potential for overlap but this is strongly timevarying. Eastern (also known as central) Baltic cod spawn at a different time to the western Baltic stock, now preferring summer to spring (Wieland et al. 2000). The spawning locations are in deep waters to the south (Bornholm Basin and Slupsk Furrow) with sufficient salinity for fertilization and buoyancy (ICES 2009a). The overlap with herring in this region has been investigated by (Köster and Möllmann 2000).

Baltic sprat is a very large stock with a wide distribution in both coastal and offshore areas of ICES subdivisions 22-32 (ICES 2009a). The overlap between cod eggs and sprat populations has previously been established by (Köster and Möllmann 2000).


Literature Cited

Bagge, O., E. Thurow, E. Steffensen, and J. Bay. 1994. The Baltic cod. Dana 10:1–29.

Bierman, S. M., M. Dickey-Collas, C. J. G. van Damme, H. M. J. van Overzee, M. G. Pennock-Vos, S. V. Tribuhl, and L. A. W. Clausen. 2010. Between-year variability in the mixing of North Sea herring spawning components leads to pronounced variation in the composition of the catch. ICES Journal of Marine Science 67:885–896.

Brander, K. 1994. The location and timing of cod spawning around the British Isles. ICES Journal of Marine Science 51:71–89.

Bundy, A., and L. P. Fanning. 2005. Can Atlantic cod (Gadus morhua) recover? Exploring trophic explanations for the non-recovery of the cod stock on the eastern Scotian Shelf, Canada. Canadian Journal of Fisheries and Aquatic Sciences 62:1474–1489.

Cushing, D. H., and J. P. Bridger. 1966. The stock of herring in the North Sea, and changes due to fishing. Fishery Investigations London, Ser II 25:1–123.

Daan, N., A. D. Rijnsdorp, and G. R. van Overbeeke. 1985. Predation by North Sea Herring Clupea harengus on Eggs of Plaice Pleuronectes platessa and Cod Gadus morhua. Transactions of the American Fisheries Society 114:499–506.

Devold, F. 1963. The life history of the Atlanto-Scandian herring. Rapports et Procés - Verbaux des R&ecaute;unions, Conseil Permanent International Pour L'Exploration de la Mer 154:98–108.

Dragesund, O., A. Johannessen, and Ø. Ulltang. 1997. Variation in migration and abundance of Norwegian spring spawning herring (Clupea harengus L.). Sarsia 82:97–105.

Duplisea, D. E., and D. Robert. 2008. Prerecruit survival and recruitment of northern Gulf of St Lawrence Atlantic cod. ICES Journal of Marine Science 65:946–952.

Fox, C. J., C. M. O'Brien, M. Dickey-Collas, and R. D. M. Nash. 2000. Patterns in the spawning of cod (Gadus morhua L.), sole (Solea solea L.) and plaice (Pleuronectes platessa L.) in the Irish Sea as determined by generalized additive modelling. Fisheries Oceanography 9:33–49.

Fox, C. J., M. Taylor, M. Dickey-Collas, P. Fossum, G. Kraus, N. Rohlf, P. Munk, C. J. G. van Damme, L. J. Bolle, D. L. Maxwell, and P. J. Wright. 2008. Mapping the spawning grounds of North Sea cod (Gadus morhua) by direct and indirect means. Proceedings of the Royal Society B: Biological Sciences 275:1543–1548.

Frank, K. T., B. Petrie, J. S. Choi, and W. C. Leggett. 2005. Trophic cascades in a formerly coddominated ecosystem. Science 308:1621.

Garrison, L. P., W. Michaels, J. S. Link, and M. J. Fogarty. 2002. Spatial distribution and overlap between ichthyoplankton and pelagic fish and squids on the southern flank of Georges Bank. Fisheries Oceanography 11:267–285.

ICES. 2005. Spawning and life history information for North Atlantic cod stocks. ICES Cooperative Research Report 274:152pp.

ICES, 2008a. Report of the Working Group on the Assessment of Northern Shelf Demersal Stock (WGNSDS), 15-21 May 2008, Copenhagen, Denmark. Technical report, International Council for the Exploration of the Sea.

ICES, 2008b. Report of the Working Group on the Assessment of Southern Shelf Dermersal Stocks (WGSSDS), April 30–May 6, 2008, Copenhagen, Denmark. Technical report, International Council for the Exploration of the Sea.

ICES, 2009a. Report of the Baltic Fisheries Assessment Working Group (WGBFAS), 22–28 April 2009, ICES Headquarters, Copenhagen. Technical report, International Council for the Exploration of the Sea.

ICES, 2009b. Report of the Herring Assessment Working Group for the Area South of 62 N, 17–25 March 2009, ICES Headquarters, Copenhagen. Technical report, International Council for the Exploration of the Sea.

Köster, F., and C. Möllmann. 2000. Trophodynamic control by clupeid predators on recruitment success in Baltic cod? ICES Journal of Marine Science 57:310.

Kvamme, C., L. Nøttestad, A. Fernö, O. Misund, A. Dommasnes, B. Axelsen, P. Dalpadado, and W. Melle. 2003. Migration patterns in Norwegian spring-spawning herring: why young fish swim away from the wintering area in late summer. Marine Ecology Progress Series 247:197–210.

Lockwood, S. J. 1988. The Mackerel. Its Biology, Assessment and the Management of a Fishery. Fishing Book News Ltd., Farnham, Surrey England.

Marteinsdóttir, G., B. Gunnarsson, and I. Suthers. 2000. Spatial variation in hatch date distributions and origin of pelagic juvenile cod in Icelandic waters. ICES Journal of Marine Science 57:1182.

Óskarsson, G. J., A. Gudmundsdottir, and T. Sigurdsson. 2009. Variation in spatial distribution and migration of Icelandic summer-spawning herring. ICES Journal of Marine Science 66:1762–1767.

Overholtz, W. J., and K. D. Friedland. 2002. Recovery of the Gulf of Maine-Georges Bank Atlantic herring (Clupea harengus) complex: perspectives based on bottom trawl survey data. Fisheries Bulletin 100:593-608.

Rose, G. A. 2005. Capelin (Mallotus villosus) distribution and climate: a sea "canary" for marine ecosystem change. ICES Journal of Marine Science 62:1524–1530.

Shelton, P. A., A. F. Sinclair, G. A. Chouinard, R. Mohn, and D. E. Duplisea. 2006. Fishing under low productivity conditions is further delaying recovery of Northwest Atlantic cod (Gadus morhua). Canadian Journal of Fisheries and Aquatic Sciences 63:235–238.

Swain, D. P., and A. F. Sinclair. 2000. Pelagic fishes and the cod recruitment dilemma in the Northwest Atlantic. Canadian Journal of Fisheries and Aquatic Sciences 57:1321–1325.

Uriarte, A., and P. Lucio. 2001. Migration of adult mackerel along the Atlantic European shelf edge from a tagging experiment in the south of the Bay of Biscay in 1994. Fisheries Research 50:129–139.

Vitale, F., P. Börjesson, H. Sved¨ang, and M. Casini. 2008. The spatial distribution of cod (Gadus morhua L.) spawning grounds in the Kattegat, eastern North Sea. Fisheries Research 90:36–44.

Wieland, K., A. Jarre-Teichmann, and K. Horbowa. 2000. Changes in the timing of spawning of Baltic cod: possible causes and implications for recruitment. ICES Journal of Marine Science 57:452–464.

Wright, P. J., E. Galley, I. M. Gibb, and F. C. Neat. 2006. Fidelity of adult cod to spawning grounds in Scottish waters. Fisheries Research 77:148–158.


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